The effect of InxGa1−xN back-barriers on the dislocation densities in Al0.31Ga0.69N/AlN/GaN/InxGa1−xN/GaN heterostructures (0.05 ≤ x ≤ 0.14)

Al_0.31Ga_0.69N/AlN/GaN/In_xGa_1?xN/GaN heterostructures grown with the metal-organic chemical vapor deposition (MOCVD) technique with different In_xGa_1?xN back-barriers with In mole fractions of 0.05 ≤ x ≤ 0.14 were investigated by using XRD measurements. Screw, edge, and total dislocations, In mole fraction of back-barriers, Al mole fraction, and the thicknesses of front-barriers and lattice parameters were calculated. Mixed state dislocations with both edge and screw type dislocations were observed. The effects of the In mole fraction difference in the back-barrier and the effect of the thickness of front-barrier on crystal quality are discussed. With the increasing In mole fraction, an increasing dislocation trend is observed that may be due to the growth temperature difference between ultrathin In_xGa_1?xN back-barrier and the surrounding layers.     

Multiwall-carbon nanotube/cobalt ferrite hybrid: Synthesis,magnetic and conductivity characterization

Functionalized multiwall carbon nanotubes (MWCNT-COOH) were decorated with crystalline cobalt ferrite nanoparticles (CoFe₂O₄ NPs) by co-precipitation reaction to form MWCNT-COOH/CoFe₂O₄ hybrid. The hybrid was characterized by X-ray diffraction analysis, transmission electron microscopy (TEM), Fourier transfom infrared spectroscopy and vibrating sample magnetometry. The results confirmed that MWCNTs and CoFe₂O₄ NPs coexisted in the hybrid. The TEM results showed a thick layer of CoFe₂O₄ was intimately connected to the surface of MWCNTs. The saturation magnetization value of the hybrid was 11.5 emu/g. There has been a high frequency fluctuation in conductivity, however, above all dc conductivity changes and resulting activation energy is calculated from the Arrhenius plots. It is found to vary with the temperature regions. This can be attributed to the existence of a conventional temperature independent tunneling conduction mechanism, which can be also explained that the metallic conduction is a dominant mechanism around room temperature. The ac conductivity of MWCNT-COOH/CoFe₂O₄ hybrid might also be a consequence of the predictions of the universal dynamic response and the ‘n’ power exponents could be determined with lower concentration of the addition in the hybrids.     

Plasmon effects in electron energy loss and gain spectra in aluminium

Oberservations of the low energy secondary and Auger electron spectra and the electron energy loss spectra from a clean aluminium surface have been made and the results are compared with other recent studies including that of Jenkins and Chung (1971). Low energy emissions at 5.7 eV and 10.3 eV are associated with the creation of single electron excitations in the valence band by plasmon decay. An apparent anomaly in the plasmon loss and gain peaks associated with the Auger spectrum is discussed.     

Long-life batteries for sound level meters

The use of rechargeable, nickel-cadmium batteries instead of the throw-away type is suggested for sound level meters. The advantages are saving of money, and greater convenience in the use of sound level meters on site visits. A simple method for recharging the batteries is discussed, which should be of interest to engineers and public health inspectors, as well as acoustic specialists.     

Collective excitations in superconductors

The excitations connected with quantum condensation of a fermion gas are calculated quantitatively along the lines of a previous paper. We find exact agreement with earlier results: excitations of the phonon type in the absence of Coulomb interaction, strong indications for their nonexistence in the presence of this interaction.     

Bonding in uranium oxides: The role of 5f electrons

X-ray photoemission spectra of valence and bonding bands of UO₂, U₃O₈ and UO₃ are presented. The gradual transfer of localized 5f electrons into the bonding band as a function of oxygen content has been studied in these oxides.     

The possibility of using a semiconductor thermal probe to investigate the power flow distribution in waveguides

Conclusions

1. The temperature profile of an absorbing film for a given microwave power flux distribution has been considered.
2. The conditions under which agreement is found between the temperature relief and the flux distribution has been clarified.
3. An experimental investigation has been carried out of the temperature profile in a matched film for the TE₁₀ mode.
4. The possibility of using a semiconductor thermal probe to investigate the microwave power flux distribution has been demonstrated.